A primary use of the subject technology is free space optical communications (FSOC) and the descriptions will primarily relate to this application. However, the technology can also be applied to coherent LIDAR as well as to other optical system types, such as optical illuminators or designators.
FSOC systems can enable high-speed wireless communications over a sizable range (e.g., many kilometers). In terrestrial applications, such systems can achieve very high (e.g., more than 10 gigabits per second-Gbps) data rates. Multiplexing several (N) optical frequencies in a single system enables the data rate of the system to be multiplied by N.
Unlike communications over fiber-optic transmission lines, FSOC must deal with atmospheric turbulence. This can significantly degrade performance by creating optical phase variations across the optical aperture used to transmit and receive light. Conventional FSOC systems have a single optical aperture (“monostatic” configuration) or may have separate transmit and receive apertures (“bistatic” configuration) through which light is transmitted and received. When turbulence effects are substantial enough that the transverse scale of the phase fluctuations (typically measured by the so-called Fried parameter r0) become comparable to or smaller than the aperture diameter D then the system performance begins to degrade, resulting in signal fluctuations (fades) and/or data drop-outs. Conventional FSOC systems also typically need mechanical beam steering assemblies for coarse beam pointing as well as to mitigate pointing errors due to, for example, jitter of the platform to which it is attached. These mechanical assemblies add considerable weight, are frequently bulky, and often consume high electrical power.
The description provided in the background section should not be assumed to be prior art merely because it is mentioned in or associated with the background section. The background section may include information that describes one or more aspects of the subject technology.